Known mill drive systems comprise one or more gear stages for transmitting the drive power of an electric motor. Gear stages and electric motor in such cases form a drive train closely coupled to a working process within for example a bowl mill, a mixing drum, a crusher, a tube mill or a rotary furnace, which is subjected to considerable feedback from the working process. Usually bevel gear stages are used to link the electric motor to the drive train.
A drive facility for a mill having a vertical construction is described in DE 39 31 116 A1, in which a housing of a reduction gear is screwed firmly to the mill. In this case an exact alignment of axes of drive pinion and girth gear spaced widely apart is necessary. In addition an introduction of axial mill forces via an axial thrust bearing in a common gear housing causes significant strain for a meshing engagement of the teeth in the reduction gear. The fact that the gear space and the inner mill bearing are the same size means that the conditions are right for a rapid contamination of lubricating oil for the drive facility. In addition a mechanical power branch in the reduction gear proves problematic in view of the lack of compensation for surplus constraining forces.
A drive facility for a vertical crusher is known from JP 2005 052799 A, which is driven either via a girth gear on a rotatable base disk or via a multi-stage bevel gear. As a consequence of a lack of adjustment movement at a drive stage of the drive facility impact loads are transmitted from the working process into the drive facility, especially into its teeth area.
WO 2009/068484 A1 describes a planetary gear with one or more gear stages for driving a working machine surrounded by a girth gear, which comprises a gear housing accommodating the gear stages and a movement-adjustable toothed pinion, which meshes with the girth gear, disposed on a take-off shaft of a take-off stage. The gear housing consists of a first inherently stiff housing part and a second fixed housing part. The first housing part surrounds the take-off stage with the take-off shaft and the movement-adjustable toothed pinion and has side walls projecting beyond the gear which rest on the base. The second housing part is attached without touching the base on an end face side to the first housing part.
The older European patent application with the application file reference 09011589.0 describes a mill drive system with a gear able to be disposed below a grinding plate with at least one planetary and/or spur gear stage as well as an electric motor integrated into a housing of the gear. In addition the mill drive system comprises a converter with an assigned closed-loop control system for controlling the speed of the motor without any play in the meshing of the teeth.
A mill drive system is known from WO 2010/20287 with an integrated motor gear unit having a shared coolant circuit. The motor-gear unit is supported on a base plate of the housing surrounding the motor-gear unit.
The object of the present invention is thus to create an integrated mill drive system which makes it possible to install a motor unit in a simpler manner and to cool the motor unit efficiently.